Constant temperature CRAC control algorithm

ABSTRACT

A method of cooling including providing a fluid flow at a predetermined temperature, and adjusting at least one cooling parameter of at least one cooling device to maintain the predetermined temperature of the fluid flow when a desired mass flow of the fluid flow changes. A cooling system and further embodiments are also disclosed.

BACKGROUND OF INVENTION

1. Field of Invention

Embodiments of the invention relate generally to devices and methods for cooling electronic equipment. Specifically, aspects of the invention relate to methods of cooling electronic equipment by providing a relatively constant temperature air flow to the equipment.

2. Discussion of Related Art

Heat produced by electronic equipment can have adverse effects on the performance, reliability and useful life of the equipment. Over the years, as electronic equipment becomes faster, smaller, and more power consuming, such equipment also produces more heat, making control of heat more critical to reliable operation.

A typical environment where heat control may be critical includes a data center containing racks of electronic equipment, such as servers and CPUs. As demand for processing power has increased, data centers have increased in size so that a typical data center may now contain hundreds of such racks. Furthermore, as the size of electronic equipment has decreased, the amount of electronic equipment in each rack and power consumption of the equipment has increased. An exemplary industry standard rack is approximately six to six-and-a-half feet high, by about twenty-four inches wide, and about forty inches deep. Such a rack is commonly referred to as a “nineteen inch” rack, as defined by the Electronics Industries Association's EIA-310-D standard.

To address the heat generated by electronic equipment, such as the rack-mounted electronic equipment of a modern data center, air cooling devices have been used to provide a flow of cool air to the electronic equipment. In the data center environment, such cooling devices are typically referred to as computer room air conditioner (“CRAC”) units. These CRAC units intake warm air from the data center and output cooler air into the data center. The temperature of air taken in and output by such CRAC units may vary depending on the cooling needs and arrangement of a data center. In general, such CRAC units intake room temperature air at about 72° F. and discharge cooler air at below about 60° F.

The electronic equipment in a typical rack is cooled as the cool air is drawn into the rack and over the equipment. The air is heated by this process and exhausted out of the rack. Data centers may be arranged in various configurations depending on the purposes of the data center. Some configurations include a room-oriented configuration in which cool air is output in general to the data center room. Other configurations include a row-oriented configuration in which CRAC units and equipment racks are arranged to produce hot and cold air aisles. Still other configurations include a rack-oriented configuration in which each rack has a dedicated CRAC unit.

SUMMARY OF INVENTION

One aspect of the invention includes a method of cooling. In some embodiments, the method includes providing a fluid flow at a predetermined temperature, and adjusting at least one cooling parameter of at least one cooling device to maintain the predetermined temperature of the fluid flow when a desired mass flow of the fluid flow changes.

In some embodiments, maintaining the predetermined temperature comprises limiting an amount of change in a current output temperature of the fluid flow. In one embodiment, the amount of change is limited to two degrees Fahrenheit per minute and five degrees Fahrenheit per hour from the predetermined temperature. In one embodiment, the fluid flow includes an air flow. In some embodiments, the at least one cooling parameter includes at least one speed of a compressor of the at least one cooling device. In one embodiment, the at least one speed of the compressor corresponds to a cooling capacity of the at least one cooling device.

In some embodiments, the method further comprises changing the mass flow of the fluid flow, based on at least one representation of the desired mass flow of the fluid flow. In some embodiments, the method further comprises receiving the at least one representation of the desired mass flow of the fluid flow. In some embodiments, providing a fluid flow at the predetermined temperature includes providing the fluid flow to at least one piece of electronic equipment. In some embodiments, the at least one piece of electronic equipment is stored in at least one rack, and the method includes providing the fluid flow to the at least one rack. In some embodiments, the desired mass flow of the fluid flow is greater than a second mass flow of the fluid flow taken in by the at least one rack. In some embodiments, the desired mass flow of the fluid flow is at least as great as a second mass flow of the fluid flow taken in by the at least one rack. In some embodiments, the method includes providing the fluid flow to a data center room in which the at least one rack is disposed.

In some embodiments, the method further comprises measuring at least one physical characteristic on which the at least one representation of the desired mass flow of the fluid flow is based. In one embodiment, the at least one physical characteristic includes at least one mass flow of the fluid flow taken in by at least one housing of an object. In some embodiments, adjusting the at least one cooling parameter comprises changing at least one fan speed of the at least one cooling device based, at least in part, on the at least one representation of the desired mass flow of the fluid flow. In some embodiments, adjusting the at least one cooling parameter comprises changing the at least one fan speed of the at least one cooling device based, at least in part, on a mapping of fan speed to output mass flow of fluid. In some embodiments, adjusting the at least one cooling parameter comprises adjusting the at least one cooling parameter based on at least one stored value indicating at least one cooling parameter value. In one embodiment, the at least one stored value indicates at least one cooling parameter value corresponding to at least one of a desired cooling capacity of the at least one cooling device.

In some embodiments, the method, further comprises monitoring at least one cooling condition, and adjusting the at least one cooling parameter based on a change in the at least one cooling condition to maintain the desired mass flow of the fluid flow and the predetermined temperature. In some embodiments, the at least one cooling condition includes at least one of a current mass flow of fluid to current cooling capacity ratio, a pressure loss, a temperature, and a temperature change. In some embodiments, adjusting the at least one cooling parameter based on the change in the at least one cooling condition includes adjusting the at least one cooling parameter to avoid spikes in the mass flow of the fluid and a current output temperature of the fluid.

In one aspect, the invention includes a system for providing a fluid flow at a predetermined temperature. In some embodiments, the system comprises a cooling element configured to cool the fluid flow, a fluid moving element configured to provide the fluid flow, and a controller configured to control at least one parameter of at least one of the cooling element and the fluid moving element to maintain the fluid flow at the predetermined temperature and at a desired mass flow of the fluid.

In some embodiments, to maintain the fluid flow at the predetermined temperature, the controller is configured to limit an amount of changing in a current output temperature of the fluid flow. In some embodiments, the amount of change is less than two degrees Fahrenheit per minute and five degrees Fahrenheit per hour. In some embodiments, the fluid flow includes an air flow. In some embodiments, the cooling element includes at least one compressor, and the at least one cooling parameter includes at least one speed of the compressor. In some embodiments, the controller is configured to receive at least one indication of the desired mass flow of the fluid.

In some embodiments, the fluid moving element is configured to provide the fluid flow to at least one piece of electronic equipment. In some embodiments, the at least one piece of electronic equipment is stored in at least one rack. In some embodiments, the desired mass flow of the fluid is greater than a mass flow range of a second mass flow of the fluid taken in by the at least one rack. In some embodiments, the desired mass flow of the fluid is at least as great as a second mass flow of the fluid taken in by the at least one rack. In some embodiments, the fluid moving element is configured to provide the fluid flow to a data center room in which the at least one rack is disposed. In some embodiments, the system further comprises a sensor configured to measure at least one physical characteristic and transmit a representation of the at least one physical characteristic to the controller, and wherein the at least one indication of the desired mass flow includes the representation. In some embodiments, the at least one physical characteristic include at least one volume of the fluid flow taken in by at least one housing of at least one object. In some embodiments, the at least one object includes at least one piece of electronic equipment and the housing includes at least one rack. In some embodiments, the fluid moving element includes at least one fan. In some embodiments, the controller is configured to control the at least one parameter of the cooling element based on at least one stored value indicating at least one parameter value. In some embodiments, the at least stored value indicates the at least one parameter value corresponding to at least one available cooling capacity of the cooling element. In some embodiments, the controller is configured to control the at least one parameter of the fluid moving element based on at least one stored value indicating at least one parameter value. In some embodiments, the at least stored value indicates the at least one parameter value corresponding to at least one available mass flow of fluid from the fluid moving element. In some embodiments, the controller is further configured to adjust at least one of the at least one parameter of the cooling element and the at least one parameter of the fluid moving element based on at least one monitored cooling condition to maintain the predetermined temperature and provide the desired mass flow of the fluid. In some embodiments, the at least one cooling condition includes at least one of a current mass flow of fluid to current cooling capacity ratio, a pressure loss, a temperature, and a temperature change. In some embodiments, the controller is configured to adjust the at least one of at least one parameter of the cooling element and the at least one parameter of the fluid moving element based on the at least one monitored cooling condition to maintain the predetermined temperature and provide the desired mass flow of the fluid without temperature and mass flow of fluid spikes. In some embodiments, the system further comprises at least one sensor configured to measure the at least one cooling condition and transmit a representation of the cooling condition to the controller.

In one aspect, the invention comprises a method of cooling at least one equipment rack with a fluid flow. In some embodiments, the method comprises generating at least one first stored value indicating at least one first cooling parameter value for a cooling device configured to generate the fluid flow, providing the fluid flow from the cooling device at a first predetermined temperature and a first output mass flow of the fluid flow, measuring a change in an intake mass flow to the at least one equipment rack, determining a first chosen cooling parameter value from the at least one first stored value, wherein the cooling device using the first chosen cooling parameter value generates a second mass flow of the fluid flow that is closer to the intake mass flow than the first mass flow of the fluid flow, generating at least one second stored value indicating at least one second cooling parameter value for the cooling device, determining a second chosen cooling parameter value from the at least one second stored value, wherein the cooling device using the second chosen cooling parameter value and the first chosen cooling parameter value maintains the predetermined temperature of the fluid flow and the second mass flow of the fluid flow, and adjusting the cooling device to use the first and second chosen cooling parameter values.

In some embodiments, the method further comprises monitoring at least one physical characteristic, and adjusting at least one of the first and second cooling parameter values, based, at least in part, on the monitored physical characteristic so that the cooling device generates a third mass flow of the fluid flow that is closer to the intake mass flow than the second mass flow of fluid. In some embodiments, maintaining the predetermined temperature includes limiting an amount of change in a current temperature of the fluid flow. In some embodiments, the amount of change includes a change of two degrees Fahrenheit per minute and five degrees Fahrenheit per hour. In some embodiments, the fluid flow includes an air flow. In some embodiments, the first cooling parameter includes a fan speed and the second cooling parameter includes a compressor speed.

The invention will be more fully understood after a review of the following figures, detailed description and claims.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:

FIG. 1 is a perspective view of a cooling unit of an embodiment of the invention without an external housing;

FIG. 2A-D are four views showing data center configurations with each data center configuration being cooled in accordance with an embodiment of the invention;

FIG. 3 is a diagram of components of a cooling unit in accordance with an embodiment of the invention;

FIG. 4 is a flow chart showing the control of a cooling device in accordance with an embodiment of the invention; and

FIGS. 5A and 5B illustrate mappings of cooling information in accordance with an embodiment of the invention.

DETAILED DESCRIPTION

This invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” “having,” “containing,” “involving,” and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

In one aspect of the invention, it is recognized that thermal stress from temperature fluctuations experienced by electronic equipment may have an adverse affect on the performance, reliability, and useful life of the electronic equipment. In particular, disposing CRAC units in a data center room near equipment racks (e.g., in row-oriented and rack-oriented arrangements) may increase the temperature fluctuations experienced by the electronic equipment in the equipment racks (e.g., compared to room-oriented arrangements). It may be critical in such arrangements to control the fluctuation of temperature experienced by the electronic equipment to maintain the proper functionality of the electronic equipment.

In general, at least one embodiment of the invention is directed at cooling an object with a constant temperature fluid flow to prevent thermal stressors from damaging such electronic equipment. The object may include electronic equipment that may be damaged by temperature fluctuations. In at least one embodiment of the invention, the temperature of the fluid may be maintained by appropriately adjusting cooling parameters of the cooling device based on monitored physical characteristics and mapped relationships.

At least one embodiment of the invention is directed at using a CRAC unit to cool an air flow to electronic equipment. Examples of such CRAC units are disclosed in detail in U.S. patent application Ser. No. 11/335,874 filed Jan. 19, 2006 and entitled “COOLING SYSTEM AND METHOD,” Ser. No. 11/335,856 filed Jan. 19, 2006 and entitled “COOLING SYSTEM AND METHOD,” Ser. No. 11/335,901 filed Jan. 19, 2006 and entitled “COOLING SYSTEM AND METHOD,” Ser. No. 11/504,382 filed Aug. 15, 2006 entitled “METHOD AND APPARATUS FOR COOLING,” and Ser. No. 11/504,370 filed Aug. 15, 2006 and entitled “METHOD AND APPARATUS FOR COOLING” which are hereby incorporated herein by reference. One embodiment of a CRAC unit 101 is illustrated in FIG. 1. As shown, the CRAC unit 101 includes a rack 103 configured to house the components of the CRAC unit 101 in the manner described below.

Some implementations of the invention may include InRow RP Chilled Water Systems available from APC, Corp., West Kingston, R.I., Network AIR IR 20 KW Chilled Water Systems available from APC, Corp., West Kingston, R.I., FM CRAC Series Systems available from APC, Corp., West Kingston, R.I., and/or any other heating or precision cooling equipment.

In one embodiment of the invention, the CRAC unit 101 may include an evaporator 105 configured to cool air. The evaporator 105 may include multiple evaporator coils that may increase a surface area of the evaporator 105. A coolant may flow within the evaporator 105 (e.g., within the evaporator coils) in a liquid form. As air is drawn over the evaporator 105 (e.g., over or through the evaporator coils), the air may be cooled by the coolant. The coolant, conversely, may be warmed by the air as the air is drawn over the evaporator 105 thereby causing the coolant to evaporate.

In some embodiments of the invention, the air may be drawn across the evaporator 105 by one or more fans, each indicated at 107. The fans 107 may be arranged to pull warm air into the CRAC unit 101 from a direction indicated by arrows A, move the air over the evaporator 105 so that the air is cooled, and then exhaust the cooled air from the CRAC unit 101 in a direction indicated by arrows B. As illustrated in FIG. 1, a plurality of fans 107 may be used to draw the air through CRAC unit 101.

Fan 107 may be configured to adjust or otherwise vary their speed to increase or decrease the volume of air drawn through the CRAC unit 101 over the evaporator 105. As the fan speed increases, a larger air mass flow may be drawn through the CRAC unit 101. Conversely, as the fan speed decreases, a smaller air mass flow may be drawn through the CRAC unit 101. The fan speed may be controllable by a controller coupled to the CRAC unit 101, as described below.

It should be appreciated that in other implementations of a CRAC unit (e.g., 101), fans (e.g., 107) may be replaced or supplemented with one or more other fluid moving or directing devices, including pumps, pipes, directing surfaces, tubes, etc. Fluid moving devices may be fully variable, semi-variable or non-variable. When the term “fan” is used herein it should be understood to include any fluid moving and/or directing device, including fans, pumps, pipes, tubes, directing surfaces, etc. When the term “fan speed” is used herein, it should be understood to include any regulator of a mass flow of fluid being moved by any fluid moving device. In one implementation, a fan may include a dedicated controller configured to adjust fan speed based on an input signal indicating a measured temperature or other cooling condition or parameter. The term “mass flow” should be understood to include any indication of a volume over a period of time.

In one embodiment, the CRAC unit 101 may further include a condenser 109 configured to cool the coolant as cool air is drawn across the condenser 109. The condenser 109 may include multiple condenser coils to provide a large operational surface area for the condenser 109. The coolant may flow within the condenser 109 (e.g., within the condenser coils) in a gaseous form. As air is drawn over the condenser 109 (e.g., over or through condenser coils) the coolant may be cooled by the air thereby causing the coolant to condense. The air drawn over the condenser may be warmed by the coolant and exhausted from the CRAC unit 101. In one embodiment, air may be drawn into the CRAC unit 101 through a plenum along arrow C so as to move the air over the condenser 109 and out of the unit along an air path defined by arrows D. Fans may be provided to achieve the air flow over the condenser 109 as described above.

In one embodiment, the flow of the coolant through and between the evaporator 105 and the condenser 109 may be facilitated by a compressor 111. The compressor 111 may pump coolant through pipes coupling the compressor 111 to the evaporator 105 and the condenser 109 so that the coolant is warmed in the evaporator 105 as it cools air and is cooled in the condenser 109 as it warms air.

The speed at which the compressor 111 pumps the coolant through the evaporator 105 may determine a cooling capacity of the CRAC unit 101 (i.e., amount of heat removed from the air by the CRAC unit 101 over a period of time as the air moves over the evaporator 105). If more coolant is pumped to the evaporator 105, the evaporator 105 may remove a greater amount of heat from the air flowing over it. If less coolant is pumped to the evaporator 105, the evaporator 105 may remove a smaller amount of heat from the air flowing over it.

In some implementations, a compressor (e.g., 111) may be fully variable between a minimum and maximum coolant flow rate. In other implementations, a compressor (e.g., 111) may be non-variable or semi-variable allowing one or a few discrete coolant flow rates. In still other implementations, a compressor (e.g., 111) may be configured as a matrix of multiple compressors acting collectively to control the flow rate. It should be appreciated that the invention is not limited to any specific compressor configuration listed above or otherwise. The flow rate of a compressor (e.g., 111) may be controlled by a controller coupled to the CRAC unit 101, as described below.

In one embodiment, the CRAC unit 101 may include or be coupled to one or more sensors 113 to measure one or more physical characteristics of the air flow through the CRAC unit 101. The sensors 113 may include relative humidity sensors, temperature sensors, pressure sensors, absolute humidity sensors, and/or any other desired sensors, as discussed in more detail below. The sensors 113 may be disposed in the CRAC unit 101, as illustrated in FIG. 1, in a data center room in general, and/or in an electronic equipment rack. The purpose of the sensors 113 will become apparent as the description of embodiments of the invention proceeds.

FIGS. 2A-2D illustrate some exemplary configurations of various CRAC units in accordance with various embodiments of the invention. As discussed, CRAC units, such as the CRAC unit 101 shown in FIG. 1, are typically disposed in a data center room. FIG. 2A illustrates a room-based arrangement in which CRAC units 201, 203, 205, and 207 are disposed near the edge of a data center room and provide general cooling to the entire room, which is filled with rows of equipment racks, each equipment rack being indicated at 209. FIG. 2B illustrates a rack-based arrangement in which a CRAC unit 211 is coupled to an equipment rack 213 to provide dedicated cooling to that specific equipment rack 213. FIG. 2C illustrates a row-based arrangement in which equipment racks, each indicated at 217, form hot aisles and cold aisles. CRAC units 215, which are interspersed within the equipment racks 215, intake hot air exhausted by the equipment racks 217 from the hot aisles and output cold air to the cold aisles to cool the equipment racks 217. In such a configuration, equipment racks and CRAC units may be arranged in any ratio (e.g., two equipment units for every one CRAC unit, etc). FIG. 2D illustrates an alternative row-based arrangement in which CRAC units 219 and 221 are disposed along the ceiling of a data center room. The CRAC units 219 and 221 and the rows of equipment racks 223, 225, 227, and 229 of FIG. 2D form hot and cold aisles.

It should be appreciated that the above illustrations of the CRAC unit 101 of FIG. 1 and CRAC unit arrangements (e.g., FIGS. 2A-D) are given as examples only. Embodiments of the invention are not limited to any particular arrangement of CRAC units or any particular CRAC unit. Furthermore, embodiments of the invention are not limited to CRAC units but, rather, may include any cooling device configured to cool any object with any fluid, including any gas and/or liquid.

FIG. 3 illustrates a block diagram of some components of a cooling device (e.g., a CRAC unit 101) according to at least one embodiment of the invention. As described in more detail below, FIG. 3 illustrates a controller 301, one or more controlled devices 305, 307, and one or more sensors 309, 311, 313, 315 coupled by a communication network 303.

In one embodiment, the controller 301 may be dedicated to a single cooling device (e.g., CRAC unit 101). In another embodiment, the controller 301 may control a plurality of cooling devices (e.g., the controller 301 may be part of a main data center control system or a dedicated cooling system). In one embodiment, the controller 301 may include a Philips XAG49 microprocessor, available commercially from the Phillips Electronics Corporation North America, New York, N.Y. The controller 301 may include a volatile memory and a static memory that may store information such as executable programs and other data useable by controller 301. The controller 301 may be coupled to an external memory device, such as a hard disk drive (not shown) that may also store executable programs and other data usable by the controller 301. In one embodiment, the controller 301 may communicate with other components of the cooling device over a network 303. The network 303 may include an internal cooling device bus, a local area network, and/or a wide area network. The network 303 may include a wired portion (e.g., a portion including a mechanical connection between two points) and/or a wireless portion (e.g., a portion without a mechanical connection between two points, such as a Wi-Fi network).

As illustrated in FIG. 3, in one embodiment, the network 303 may couple the controller 301 to one or more controlled devices (e.g., 305 and 307) that regulate a cooling parameter (e.g., compressor speed, fan speed, etc.) of a cooling unit (e.g., 101). In one embodiment, the one or more devices include a compressor 305 and/or a fan 307. The controller 301 may communicate over the network 303 to adjust a parameter of the compressor 305 and/or the fan 307. For example, the controller 301 may transmit a control signal to the compressor 305 indicating a change in compressor speed. The compressor 305 may receive the control signal from the network 303 and adjust the speed of coolant flow accordingly. As another example, the controller 301 may transmit a control signal to the fan 307 indicating a change in fan speeds. The fan 307 may receive the control signal from the network 303 and adjust its speed accordingly.

In one embodiment, the controller 301 may execute one or more control loops (e.g., proportional-integral-derivative (PID) loops) written in a firmware of the controller 301 to determine when and which control signals should be transmitted to controlled devices (e.g., 305 and 307). In one embodiment, one control loop executed by the controller may generate an input for another control loop executed by the controller. In one embodiment, the controller 301 may include multiple controllers coupled together. Each controller may execute one or more control loops. Each control loop may generate an input for one or more other control loops executed by one of the other controllers and/or one or more control signals for one or more controlled devices.

The control signals may be transmitted to adjust one or more cooling parameters (e.g., fan speed, compressor speed, etc.) so that a desired cooling output or other cooling condition may be maintained by the cooling device, such as a constant temperature, a constant air mass output, an air output volume that matches an air intake volume of a cooled device, etc. Such a desired condition, for example, may be entered by a user of the cooling device (e.g., a data center administrator) through a control panel coupled to the controller 301.

In one embodiment of the invention, the controller 301 may be configured to maintain an output air mass flow that roughly matches an air mass flow taken in by the electronic equipment being cooled by the cooling device. In one embodiment, controller 301 may receive an input signal indicating an air mass flow taken in by the electronic equipment (e.g., from one or more sensors in or out of the CRAC unit). As discussed in more detail below, the controller 301 may determine a needed fan speed to match the air mass flow taken in by the electronic equipment. A matching air mass flow may include an air mass flow greater than the intake air mass flow and/or an air mass flow within a range of the intake air mass flow. The controller 301 may then generate one or more control signals to adjust a fan speed of the controlled devices (e.g., 305, 307) so that the air mass flow output by the cooling device (e.g., CRAC unit 101) matches the air mass flow of air taken in by the electronic equipment. As discussed below, controller 301 may be configured to adjust other cooling parameters (e.g., the compressor speed) to maintain a predetermined temperature of the air flow to the electronic equipment as the fan speed and/or other characteristics of the environment change (e.g., dust, wear and tear, efficiency, etc.).

To facilitate proper control of cooling parameters, in one embodiment, the controller 301 may be coupled to one or more sensors 309, 311, 313, and 315. The sensors 309, 311, 313, and 315 may measure physical characteristics or other information relevant to determining which control signals to send to controlled devices (e.g., 305, 307) and transmit a representation of the measured characteristics to the controller 301 through the network 303. The sensors 309, 311, 313, and 315 may include temperature sensors 309, relative humidity sensors 311, pressure sensors 313, and any other sensors 315 that may measure any physical characteristic relevant to the control of a cooling device. The sensors 309, 311, 313, and 315 may be disposed within a CRAC unit (e.g., 101) or other cooling device, generally in a data room, in cooled equipment racks, or any other desired location.

In one aspect of the invention, it is recognized that the cooling parameters of the cooling device may be controlled to provide a predetermined temperate air flow to the electronic equipment even as air mass flow provided to the electronic equipment and/or other cooling conditions change. As discussed above, maintaining a temperature of the air flow may prevent thermal stress on the electronic equipment from having adverse effects on the performance, reliability, and useful life of the equipment. An example process 400 that may be performed to maintain the temperature is illustrated in FIG. 4. The process 400 may be widely deployable and both reliably and predictably deliver air at a predetermined and/or constant temperature. Furthermore, process 400 may be based on easily understandable principals to improve the speed of deployment since those involved in deployment may readily understand the underlying principals.

It should be appreciated that when the terms predetermined temperature and/or constant temperature are used herein, the terms may refer to a temperature within a temperature range of a target temperature so that the electronic equipment does not experience large variations in temperature. Although in some embodiments the temperature may be absolutely constant, in other embodiments, the temperature may vary within the range of acceptable temperature. In one implementation, the target temperature may include about sixty-eight degrees Fahrenheit. In one implementation, the range may include a percentage of the target temperature (e.g., about ten percent above and/or below the target temperature). In one implementation, the range may include a number of degrees (e.g., five degrees Fahrenheit). In one implementation, the temperature range may include a change in temperature over time. In one implementation the temperature range may include a change of about five degrees Fahrenheit per hour and about two degrees Fahrenheit per minute.

In one embodiment, process 400 may begin by generating one or more mappings of cooling parameters as indicated in block 401. The cooling parameters may include one or more of a fan speed, a compressor speed, a compressor frequency, a signal to or from a fluid or refrigerant flow valve, and signal indicating a mass flow of fluid or air temperature. These parameters may be mapped to any number of desired other parameters, cooling conditions, and/or physical characteristics. Some example mappings are illustrated in FIGS. 5A and 5B. These mappings may be generated in a lab environment to mirror the physical world that may be experienced by the cooling unit in operation. In other embodiments, these mappings may be computed based on characteristics of the cooling device and/or may be determined using a computer simulation.

In one embodiment, the mappings may be generated before the cooling device is installed in a data center room. In one embodiment, the mappings may be generated during the manufacture and/or design of a cooling device (e.g., CRAC unit 101). The mappings may describe the relationship between a cooling parameter and one or more variables, for example, in a graph or table.

The mappings may be generated, for example, by varying input characteristics and the parameter and monitoring the output of the cooling unit. For example, fan speed may be mapped to air mass flow by measuring the output air mass flow while adjusting the fan speed. The measured output air mass flow may be recorded, for example, in a table such as table 501 of FIG. 5A. As another example, the compressor speed may be mapped to cooling capacity by measuring the output cooling capacity while adjusting the compressor speed. The output cooling capacity may be determined, for example by comparing a temperature of an air flow taking in by the cooling unit to the temperature of cooled air flow output by the cooling unit. The measured cooling capacity may be recorded, for example, in a table such as table 503 of FIG. 5B. It should be appreciated that each mapping may include a dimension for each variable on which the parameter or condition is being mapped.

For example, in one embodiment, fan speed may be mapped to a desired output mass flow of air, a pressure loss over a filter of the cooling device, a pressure loss over other portions of the cooling device, and/or any other desired characteristics. A mapping may include a dimension for each of these variables.

In one embodiment, for example, compressor speed may be mapped to cooling capacity, air mass flow, suction pressure of a CRAC unit (e.g., 101), discharge pressure of a CRAC unit (e.g., 101), a ratio of air mass flow to cooling capacity, and/or any other desired characteristic. It should be appreciated that any mapping may include any number of dimensions corresponding to any variables that may affect the mapped value, including, physical characteristic, cooling conditions, and/or cooling parameters.

In one embodiment, rather than mapping the parameters in a table or graph, one or more parameters may be defined by one or more mapping functions or equations. Such mapping functions may describe the relationship between the variables and the parameter. In one implementation, the mapping function may be derived from values obtained through the mapping process described above (e.g., a polynomial or other function derived from mapped points on a graph such as by well-known interpolation methods). It should be recognized that any set of stored values (e.g. mapped values, equations, etc.) from which a parameter value may be derived may be used in some embodiments of the present invention.

In one embodiment, as indicated in block 403, a CRAC unit (e.g., 101) may receive an indication of a target temperature at a target position, for example, from a data center administrator. In one embodiment, the target temperature may represent a target output temperature of the CRAC unit. In one embodiment, the target temperature may represent a target temperature at which the electronic equipment may be ideally cooled. In one embodiment, the target temperature may be measurable by a target sensor disposed at or near the target position.

In one embodiment, as indicated in block 405, a CRAC unit (e.g., 101) may begin producing an initial air flow to the electronic equipment with an air mass flow that matches the intake air mass flow of the electronic equipment and at a temperature that matches the target temperature. Sensors may measure various physical conditions that may be used by the CRAC unit (e.g., 101) to determine the initial cooling parameters (e.g., fan speed and compressor speed) to generate this initial air flow. For example, an intake air mass flow may be measured and used to determine a fan speed by reference to a fan speed mapping, as described in more detail below. A desired cooling capacity may be determined from measured temperature sensors and be used to determine a compressor speed from a compressor speed mapping, as described in more detail below.

In one embodiment, as indicated in block 407, sensors (e.g., 309, 311, 313, and 315) may measure a current air mass flow taken in by a cooled electronic equipment rack that differs from the initial air mass flow of block 405. The sensors (e.g., 309, 311, 313, and 315) may also measure temperatures, pressures, and/or any other measured characteristics needed to adjust cooling parameters as described below. The sensors (e.g., 309, 311, 313, and 315) may transmit an indication of the change in air mass flow and/or any other characteristics to the CRAC unit (e.g., 101) and/or CRAC unit controller (e.g., 301). The indication may include a pressure at or near a fan of the electronic equipment rack from which the intake air mass flow may be determined. The indication may include a direct indication of the air mass flow from, for example, an air mass flow sensor.

In one embodiment, as indicated in block 409, a CRAC unit (e.g., 101) and/or CRAC unit controller (e.g., 301) may receive the indication of a current air mass flow transmitted in block 407. The CRAC unit (e.g., 101) and/or CRAC unit controller (e.g., 301) may also receive the indications of other characteristics transmitted in block 407.

In one embodiment, as indicated in block 411, a CRAC unit (e.g., 101) may determine a new fan speed based on the indication of the intake air mass flow and the other measured characteristics from block 409. The fan speed may be determined from a mapping of the fan speed to output air mass flow so that the output air mass flow of the CRAC unit matches the intake air mass flow of the electronic equipment. For example, an intake air mass flow of 450 meter³/hour may be indicated. The CRAC unit may reference table 501 of FIG. 5A, for example, to determine that a fifty percent fan speed may generate the desired air mass flow of 450 m³/h.

In one embodiment, a new fan speed may be determined such that the desired output air mass flow is adjusted gradually towards the measured air mass flow rather than immediately to the measured air mass flow. For example, a measured air mass flow may be averaged with measured air mass flows over a period of time to determine an average air mass flow. Rather than the current air mass flow, the average air mass flow may be used to determine a new fan speed. Such averaging may prevent momentary spikes or drops in air mass flow, for example, from dust or debris moving by a sensor, from having a drastic effect on the cooling parameters of the CRAC unit.

In one implementation, a first controller may determine a desired air mass flow based, at least in part, on the measured air mass flow. As described above, the first controller may average the current air mass flow with the measured air mass flows. The first controller may transmit a representation of the desired air mass flow to a second controller. In one implementation, the second controller may receive the representation and determine the desired fan speed based on the desired air mass flow by referencing an appropriate mapping, as described above. It should be appreciated that although embodiments in which two separate controllers are used to perform these actions, in other embodiments, a single controller may be used to perform such action or other desired action to generate a predetermined temperature cooling output.

In one embodiment, as indicated in block 413, a CRAC unit may determine current and desired air mass flow to cooling capacity ratios. An air mass flow to cooling capacity ratio may be indicative of a temperature of an air flow output by the CRAC unit.

In one embodiment, the current air mass flow to current cooling capacity ratio may be determined according to:

$\begin{matrix} {{\frac{m_{c}}{Q_{c}} = \frac{1}{k*\left( {T_{r} - T_{s}} \right)}},} & (1) \end{matrix}$

where

$\frac{m_{c}}{Q_{c}}$

represents the current air flow to current cooling capacity ratio; k represents the specific heat of air; T_(r) represents a current temperature of air taken in for cooling by the CRAC unit (e.g., 101); T_(s) represents a current temperature of air supplied by the CRAC unit to cool the electronic equipment. T_(s) may correspond to the current temperature of output air from the CRAC unit (e.g., 101), the temperature of air taken in by the electronic equipment, or some other temperature of air at or near a target location, measured, for example, by a temperature sensor disposed at or near the target location.

In one embodiment, the desired air mass flow to desired cooling capacity ratio may be determined according to:

$\begin{matrix} {{\frac{m_{d}}{Q_{d}} = \frac{1}{k*\left( {T_{r} - T_{st}} \right)}},} & (2) \end{matrix}$

where

$\frac{m_{d}}{Q_{d}}$

represents the desired air mass flow to current cooling capacity ratio; k represents the specific heat of air; T_(r) represents a current temperature of air taken in by the CRAC unit (e.g., 101) for cooling; T_(st) represents a desired temperature of air supplied by the CRAC unit (e.g., 101) for cooling the electronic equipment. T_(st) may correspond to the desired temperature of output air from the CRAC unit, the temperature of air taken in by the electronic equipment, or some other temperature of air at a target location measured by a target sensor.

In one implementation of the invention, the current and desired air mass flow to current cooling capacity ratios may be determined by a first controller. The first controller may execute a slow PID such that a new desired air mass flow to cooling capacity ratio is generated by the slow PID that is between the current air mass flow to current cooling capacity ratio and desired air mass flow to current cooling capacity ratio. Rather than continuing the process with the desired air mass flow to current cooling capacity ratio, the process may continue with the new air mass flow to current cooling capacity ratio.

Such an implementation may prevent temporary spikes and drops in measured values from having a drastic effect on the output of a CRAC unit (e.g., 101) by producing gradual adjustments in the cooling parameters. Such temporary spikes may occur, for example, because a large piece of dust or debris blocks a sensor of the cooling device, an administrator moves near a temperature sensor, etc.

As indicated in block 415, a compressor speed needed to generate the desired air mass flow to desired cooling capacity ratio may be determined. The ratio may describe a new air mass flow that may be generated by the CRAC unit when the fan speed is adjusted to the new speed determined in block 411 and a new cooling capacity, as described below. In one embodiment, the new air mass flow may be set at a target air mass flow that matches the intake air mass flow. In one embodiment, as described above, the new air mass flow may be set at the air mass flow used to determine a fan speed in block 411. The new cooling capacity may then be determined from the new air mass flow to new cooling capacity ratio according to:

$\begin{matrix} {{Q_{n} = \frac{m_{n}}{\left\lbrack \frac{m_{d}}{Q_{d}} \right\rbrack}},} & (3) \end{matrix}$

where Q_(n) equals the new cooling capacity; m_(n) equals the new air mass flow that matches the intake air mass flow of the electronic equipment or other air mass flow used in block 411 to determine a new fan speed, as described above;

$\frac{m_{d}}{Q_{d}}$

equals the desired air mass flow to desired cooling capacity ratio.

A compressor speed that corresponds to the new cooling capacity Q_(n) may be determined by referencing a mapping of cooling parameters to cooling capacity. For example, a compressor speed may be determined from the mapping of table 503 by referencing a cooling capacity that corresponds to Q_(n). As described above, the mapping may include additional parameters that may be measured in block 407. As shown, by increasing the compressor speed, the cooling capacity also increases.

It should be appreciated that because many characteristics such as temperature, cooling capacity and pressure may be continuous, a given mapping may not include every value of such variables. In some embodiments, this may apply to a cooling capacity mapping and/or a fan speed mapping, such as the one used in block 405. In one implementation, if a value of a measured characteristic is not included in a mapping, a closest neighboring value of that characteristic may be used in its place. For example, in table 503, if new cooling capacity equaled 18000 Watts, the compressor speed of seventy-eight percent may be chosen since the mapped cooling capacity value 18005 W is closest to the desired new cooling capacity value 18000 W. In other implementations, the closest neighboring that is higher than the measured value may be used. In other implementations, the closest neighboring value that is lower than the measured value may be used. In still other implementations, a numerical method may be used to extrapolate a parameter value of the mapped parameter from neighboring values. For example, in one implementation, an average value of one or more neighboring values may be used. It should be appreciated that the invention is not limited to any particular process of determining a parameter value from a measured variable.

In one implementation, the determination of cooling parameters may be performed by a second controller of the CRAC unit (e.g., 101). The second controller may receive an indication of the desired air mass flow to cooling capacity ratio, for example, from a first controller as described above, and determine the compressor speed value based on that input along with other sensor input received by the CRAC unit (e.g., 101), as described above. In one implementation, the second controller may also receive an indication of the new air mass flow determined in block 411, as described above. With this received information from the first controller and sensors, the second controller may determine a new compressor speed by reference to one or more mappings, as described above.

In one embodiment, as indicated in block 417, a CRAC unit (e.g., 101) may then adjust the cooling parameters so that they begin producing the new air mass flow and the new cooling capacity. In one embodiment, for example, CRAC unit controller (e.g., 301) may transmit control signals to the fan and compressor of the CRAC unit (e.g., 101) to adjust their fan speed and compressor speed to the newly determined values described above.

As indicated in block 419, in one embodiment, a CRAC unit (e.g., 101) may continue to monitor physical characteristics and cooling conditions. For example, the CRAC unit (e.g., 101) may monitor the current air mass flow to current cooling capacity ratio for any changes, for example, by using temperature measurements and Equation 1 above. As another example, pressure sensors may continue to measure pressure change over a filter of the cooling device. As the filter fills with dust and other particles, a pressure drop may increase. An increase in pressure drop may cause a lower air mass flow to be delivered from the cooling device to the cooled electronic equipment without a change in the fan speed of a CRAC unit (e.g., 101). The measurement of the pressure drop may be a variable in a mapping of the fan speed, so that as the pressure drop changes, the mapping may be referenced to determine a new fan speed that may be used to maintain the current air mass flow.

Such a change in one of the monitored conditions may require a fan speed change to maintain a total air mass flow provided by the CRAC unit at a level that matches the air mass flow taken in by the cooled electronic equipment. In some situations, such a change may also require a change in compressor speed to maintain an air mass flow to cooling capacity ratio.

For example, if a fan speed is changed in a way that affects the air mass flow, for example, if the fan is not fully variable and the fan is moved to a higher fan speed that corresponds to a higher air mass flow, the compressor speed may be adjusted as well to maintain the air mass flow to cooling capacity ratio. In such a circumstance, a CRAC unit (e.g., 101) may determine the new air mass flow that may result if the fan speed is adjusted. Using the new air mass flow, and the desired air mass flow to cooling capacity ratio, the CRAC unit may determine a new cooling capacity using equation 3, as described above. A mapping of compressor speed may be referenced to determine a compressor speed corresponding to the new desired cooling capacity, as described above.

In one embodiment, because measured characteristics (e.g., pressure or temperature) or monitored conditions (e.g., current air mass flow to cooling capacity ratio) may experience sudden spikes or drops from temporary conditions, as discussed above, cooling parameters may be adjusted slowly rather than immediately in response to changes in such characteristics or conditions.

For example, a CRAC unit may measure a large change in a current air mass flow to cooling capacity ratio. Rather than immediately adjusting cooling parameters to return the current air mass flow to cooling capacity ratio to the desired air mass flow to cooling capacity ratio, a CRAC unit (e.g., 101) may gradually adjust the cooling parameters from their current level to the level that may be needed to produce the desired air mass flow to cooling capacity ratio.

In one implementation, to gradually adjust the cooling parameters, a two controller system may be used, as described above. A first controller may determine a difference between the current and desired air mass flow to cooling capacity ratio. The first controller may determine a new air mass flow to cooling capacity ratio between the new and desired air mass flow to cooling capacity ratios. The first controller may transmit the new air mass flow to cooling capacity ratio to a second controller. The second controller may determine a new compressor speed based on the new air mass flow to cooling capacity ratio and the air mass flow being delivered to the electronic equipment, as described above.

If any change is determined in block 419, a CRAC unit (e.g., 101) may adjust the cooling parameters, as indicated in block 421. The cooling parameters may be adjusted by, for example, transmitting control signals for a controller (e.g., 301) to the controlled devices (e.g., 305, 307) through a network (e.g., 303), as described above.

By employing such a method, the cooling device may deliver an air flow to the cooled electronic equipment that is at a mostly constant temperature even as the air flow and other cooling parameters and physical characteristics change. It should be appreciated, however, that the invention is not limited to any particular set of steps, cooling parameters or measured characteristics.

Although embodiments of the invention have been described with respect to cooling electronic equipment in data center environments, it should be recognized that embodiments of the invention are not so limited. Rather, embodiments of the inventions may be used to provide cooling in any environment to any object and/or space. For example, embodiments of the invention may be used with telecommunication equipment in outdoor environments or shelters, telecommunication data centers, and/or mobile phone radio base-stations. Embodiments of the invention may be used to with precious goods such as art work, books, historic artifacts and documents, and/or excavated biological matters (for example, for preservation purposes). Embodiments of the invention may be used for preservation of meats, wines, spirits, foods, medicines, biological specimens and samples, and/or other organic substances. Further embodiments may be used for process optimization in biology, chemistry, greenhouse, and/or other agricultural environments. Still other embodiments may be used to protect against corrosion and/or oxidization of structures (for example, buildings, bridges, or large structures).

Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only. 

1. A method of cooling, the method comprising acts of: A) providing a fluid flow at a predetermined temperature; and B) adjusting at least one cooling parameter of at least one cooling device to maintain the predetermined temperature of the fluid flow when a desired mass flow of the fluid flow changes.
 2. The method of claim 1, wherein maintaining the predetermined temperature comprises limiting an amount of change in a current output temperature of the fluid flow.
 3. The method of claim 2, wherein the amount of change is limited to two degrees Fahrenheit per minute and five degrees Fahrenheit per hour from the predetermined temperature.
 4. The method of claim 1, wherein the fluid flow includes an air flow.
 5. The method of claim 1, wherein the at least one cooling parameter includes at least one speed of a compressor of the at least one cooling device.
 6. The method of claim 5, wherein the at least one speed of the compressor corresponds to a cooling capacity of the at least one cooling device.
 7. The method of claim 1, further comprising an act of C) changing the mass flow of the fluid flow, based on at least one representation of the desired mass flow of the fluid flow.
 8. The method of claim 7, further comprising an act of D) receiving the at least one representation of the desired mass flow of the fluid flow.
 9. The method of claim 7, wherein the act A comprises providing the fluid flow to at least one piece of electronic equipment.
 10. The method of claim 9, wherein the at least one piece of electronic equipment is stored in at least one rack, and the act A includes providing the fluid flow to the at least one rack.
 11. The method of claim 10, wherein the desired mass flow of the fluid flow is greater than a second mass flow of the fluid flow taken in by the at least one rack.
 12. The method of claim 10, wherein the desired mass flow of the fluid flow is at least as great as a second mass flow of the fluid flow taken in by the at least one rack.
 13. The method of claim 10, wherein the act A comprises providing the fluid flow to a data center room in which the at least one rack is disposed.
 14. The method of claim 7, further comprising an act of D) measuring at least one physical characteristic on which the at least one representation of the desired mass flow of the fluid flow is based.
 15. The method of claim 14, wherein the at least one physical characteristic includes at least one mass flow of the fluid flow taken in by at least one housing of an object.
 16. The method of claim 7, wherein the act C comprises changing at least one fan speed of the at least one cooling device based, at least in part, on the at least one representation of the desired mass flow of the fluid flow.
 17. The method of claim 16, wherein the act C comprises changing the at least one fan speed of the at least one cooling device based, at least in part, on a mapping of fan speed to output mass flow of fluid.
 18. The method of claim 1, wherein the act B comprises adjusting the at least one cooling parameter based on at least one stored value indicating at least one cooling parameter value.
 19. The method of claim 18, wherein the at least one stored value indicates at least one cooling parameter value corresponding to at least one of a desired cooling capacity of the at least one cooling device.
 20. The method of claim 1, further comprising acts of: C) monitoring at least one cooling condition; and D) adjusting the at least one cooling parameter based on a change in the at least one cooling condition to maintain the desired mass flow of the fluid flow and the predetermined temperature.
 21. The method of claim 20, wherein the at least one cooling condition includes at least one of a current mass flow of fluid to current cooling capacity ratio, a pressure loss, a temperature, and a temperature change.
 22. The method of claim 20, wherein the act D includes adjusting the at least one cooling parameter to avoid spikes in the mass flow of the fluid and a current output temperature of the fluid.
 23. A system for providing a fluid flow at a predetermined temperature, the system comprising: a cooling element configured to cool the fluid flow; a fluid moving element configured to provide the fluid flow; and a controller configured to control at least one parameter of at least one of the cooling element and the fluid moving element to maintain the fluid flow at the predetermined temperature and at a desired mass flow of the fluid.
 24. The system of claim 23, wherein to maintain the fluid flow at the predetermined temperature, the controller is configured to limit an amount of changing in a current output temperature of the fluid flow.
 25. The system of claim 24, wherein the amount of change is less than two degrees Fahrenheit per minute and five degrees Fahrenheit per hour.
 26. The system of claim 23, wherein the fluid flow includes an air flow.
 27. The system of claim 23, wherein the cooling element includes at least one compressor, and the at least one cooling parameter includes at least one speed of the compressor.
 28. The system of claim 23, wherein the controller is configured to receive at least one indication of the desired mass flow of the fluid.
 29. The system of claim 28, wherein the fluid moving element is configured to provide the fluid flow to at least one piece of electronic equipment.
 30. The system of claim 29, wherein the at least one piece of electronic equipment is stored in at least one rack.
 31. The system of claim 30, wherein the desired mass flow of the fluid is greater than a mass flow range of a second mass flow of the fluid taken in by the at least one rack.
 32. The system of claim 30, wherein the desired mass flow of the fluid is at least as great as a second mass flow of the fluid taken in by the at least one rack.
 33. The system of claim 30, wherein the fluid moving element is configured to provide the fluid flow to a data center room in which the at least one rack is disposed.
 34. The system of claim 28, further comprising a sensor configured to measure at least one physical characteristic and transmit a representation of the at least one physical characteristic to the controller, and wherein the at least one indication of the desired mass flow includes the representation.
 35. The system of claim 34, wherein the at least one physical characteristic include at least one volume of the fluid flow taken in by at least one housing of at least one object.
 36. The system of claim 35, wherein the at least one object includes at least one piece of electronic equipment and the housing includes at least one rack.
 37. The system of claim 23, wherein the fluid moving element includes at least one fan.
 38. The system of claim 23, wherein the controller is configured to control the at least one parameter of the cooling element based on at least one stored value indicating at least one parameter value.
 39. The system of claim 38, wherein the at least stored value indicates the at least one parameter value corresponding to at least one available cooling capacity of the cooling element.
 40. The system of claim 23, wherein the controller is configured to control the at least one parameter of the fluid moving element based on at least one stored value indicating at least one parameter value.
 41. The system of claim 40, wherein the at least stored value indicates the at least one parameter value corresponding to at least one available mass flow of fluid from the fluid moving element.
 42. The system of claim 23, wherein the controller is further configured to adjust at least one of the at least one parameter of the cooling element and the at least one parameter of the fluid moving element based on at least one monitored cooling condition to maintain the predetermined temperature and provide the desired mass flow of the fluid.
 43. The system of claim 42, wherein the at least one cooling condition includes at least one of a current mass flow of fluid to current cooling capacity ratio, a pressure loss, a temperature, and a temperature change.
 44. The system of claim 42, wherein the controller is configured to adjust the at least one of at least one parameter of the cooling element and the at least one parameter of the fluid moving element based on the at least one monitored cooling condition to maintain the predetermined temperature and provide the desired mass flow of the fluid without temperature and mass flow of fluid spikes.
 45. The system of claim 42, further comprising at least one sensor configured to measure the at least one cooling condition and transmit a representation of the cooling condition to the controller.
 46. A method of cooling at least one equipment rack with a fluid flow, the method comprising: generating at least one first stored value indicating at least one first cooling parameter value for a cooling device configured to generate the fluid flow; providing the fluid flow from the cooling device at a first predetermined temperature and a first output mass flow of the fluid flow; measuring a change in an intake mass flow to the at least one equipment rack; determining a first chosen cooling parameter value from the at least one first stored value, wherein the cooling device using the first chosen cooling parameter value generates a second mass flow of the fluid flow that is closer to the intake mass flow than the first mass flow of the fluid flow; generating at least one second stored value indicating at least one second cooling parameter value for the cooling device; determining a second chosen cooling parameter value from the at least one second stored value, wherein the cooling device using the second chosen cooling parameter value and the first chosen cooling parameter value maintains the predetermined temperature of the fluid flow and the second mass flow of the fluid flow; and adjusting the cooling device to use the first and second chosen cooling parameter values.
 47. The method of claim 46, further comprising: monitoring at least one physical characteristic; and adjusting at least one of the first and second cooling parameter values, based, at least in part, on the monitored physical characteristic so that the cooling device generates a third mass flow of the fluid flow that is closer to the intake mass flow than the second mass flow of fluid.
 48. The method of claim 46, wherein maintaining the predetermined temperature includes limiting an amount of change in a current temperature of the fluid flow.
 49. The method of claim 48, wherein the amount of change includes a change of two degrees Fahrenheit per minute and five degrees Fahrenheit per hour.
 50. The method of claim 46, wherein the fluid flow includes an air flow.
 51. The method of claim 46, wherein the first cooling parameter includes a fan speed and the second cooling parameter includes a compressor speed. 